Sterile packaging method

ABSTRACT

A sterile packaging method which involves the steps of sealing a suitable fluid or solid product within a container capable of withstanding prolonged exposure to temperatures up to 212* F., and thereafter heating the container and its contents for an extended period, but at a temperature substantially below the boiling point of water, until the container&#39;&#39;s interior surfaces and contents are sterilized.

United States Patent Moore et a].

STERILE PACKAGING METHOD Inventors: Francis C. Moore; Leon R.

Perkinson, both of Indianapolis, lnd.

Moore-Perk Corporation, Indianapolis, Ind.

Filed: Nov. 5, 1971 Appl. No.: 195,926

Related U.S. Application Data Continuation-impart of Ser. No. ll2,762,Feb. 4, l97l, which is a continuation-in-part of Ser. No. 873,786, Nov.4, I969, Pat. No. 3,6l8,283.

Assignee:

U.S. Cl 53/21 FC, 21/2, 53/25 Int. Cl 1365b 55/18 Field of Search 53/2lFC, 25; 21/2,

[ Aug. 28, 1973 [56] References Clted UNITED STATES PATENTS 2,832,6644/1958 Bloch 21/2 X 2,380,134 7/I945 Waters 2l/99 X PrimaryExaminer-Travis S. McGehee Attorney-John B. Lungmus [57] ABSTRACT 5Claims, No Drawings RELATED APPLICATIONS This application is acontinuation-in-part of our copending application Ser. No. 112,762,filed Feb. 4, l97l which in turn is a continuation-in-part of ourcopending application Ser. No. 873,786, filed Nov. 4, 1969 now US. Pat.No. 3,618,283.

BACKGROUND The aforementioned co-pending application Ser. No. 873,786discloses a method for the sterile packaging of surgical sponges andother articles in sealed flexible wrappers. During the packagingoperation, and immediately following the sealing of the wrappers, thepackages are squeezed or compressed so that all of the surfaces withinthe packages will be flushed or wetted by the germicidal soap solutioncontained within the packages. Subsequent heating at a low enoughtemperature to avoid rupturing the flexible walls of the wrappersresults in sterilization of all of the surfaces contacted by the liquidor, in other words, all of the surfaces within the packages.

Co-pending application Ser. No. 1 12,762 is concerned with the furtherdiscovery that sterilization may be achieved even where some of thesurfaces of the packages are not flushed or contacted by theantibacterial solution. A container is simply filled partially with ananti-bacterial agent solution and, after placing in the containers thoseadditional items (if any) to be sterilized, the container is sealed sothat an air (or gas) space is disposed above the liquid. Thereafter, thecontainer and its contents are heated to a temperature well below theboiling point of the liquid and at a pressure of about 1 atmosphere. Ingeneral, the temperature to which the container and its contents areheated will fall within the range of about 130 to 210 F., but usuallybelow 180 degrees F., the particular temperature selected depending uponthe anti-bacterial agent used and the duration of the heating step. Theheating operation is continued until all organisms, including spores,are killed, the interval normally falling within the range of 2 to 24hours.

SUMMARY The present invention is concerned with the further relateddiscovery that sterilization, as detennined by accepted testing methodsnow available, may be achieved even in the absence of an anti-bacterialagent if the subboiling heating step is continued long enough and if atleast some moisture is present in the container. Periods of heattreatment of 24 hours or more are involved. Since such treatment occursat a temperature substantially below the boiling point of water, thedanger or rupturing or breaking the container by reason of liquidvolatilization, or the build up of excessive internal pressure, isavoided or greatly reduced. While the method may be used in conjunctionwith rigid containers formed of material capable of withstandingtemperatures of 210 F. or even higher, it is particularly effectivewhere sterilization of the contents of bags and other flexible-walledcontainers is desired. The contents of such containers may be solid, asin the case of surgical drapes, bandages, and instruments, or may beliquid such as, for example, parenteral fluids, or may even be gaseous.Since water in either liquid or vapor state must be present in at leastlimited quantities, the

contents of the packages will in many instances consist of products orsubstances of different phases.

DESCRIPTION It is generally agreed that bacterial spores are moreresistant to thermal inactivation than other microorganisms. Theterm"sterilization" as used herein means a method wherein no organisms arefound living after treatment and in which even the most resistantorganisms (spores) give no evidence of viability following suchtreatment. The sporicidal test recommended by the Association ofOfficial Analytical Chemists and by other organizations suggest thatBacillus subtilis (Globigii) or Bacillus stearothermophilus be used, andthe tests carried out in determining the results of the presentinvention are in accordance with those recommendations.

The method involves the step of first sealing a product in a containerformed of a material capable of withstanding temperatures up to 212 F.The container may be formed of glass, metal, or any of a variety ofsuitable plastic materials which are liquid impermeable. Polyethylene,polyvinyl chloride, and polypropylene, and gas-impermeable laminates ofsuch plastics with metal foil, have been found effective. in the case ofa flexible container formed of thermoplastic material, the sealing maybe achieved by a direct application of heat (heat sealing), althoughcementing and other suitable sealing techniques may be used. Rigidcontainers may be provided with sealing caps or may be sealed by anyother means as well known in the art.

The product sealed within the container may take any of a wide varietyof forms. Quite commonly, such product will be a solid item such as asurgical sponge, garment, bed sheet, instrument, or some other articlecapable of withstanding temperatures up to 2 l 2 F. Altematively, theproduct might be a liquid or a gas. In any case, whether the contentsare solid, liquid, or gaseous, some water in either liquid or vapor formis believed essential. Where the contents of the package consistprimarily of an aqueous solution an abundance of water will obviously bepresent. Where such contents consist primarily of a solid article thenthe remaining air or gas space within the package must contain somemoisture.

After the sealing step, the container and its contents are heated to atemperature substantially below 212 F. and above a minimum temperatureof about 170 F. for a period in excess of 24 hours. The duration of theheating step depends largely on the nature of the contents and theextent of contamination prior to packaging. Heating periods of 7 days ormore may be required to achieve sterilization where the only moisturepresent is in the form of water vapor. The duration of the heating stepmay also be reduced by heating the contents at a temperature within theupper portion of the temperature range; however, care must be exercisedto maintain a temperature well below the boiling point of water. Apreferred range, subject to some variation depending upon thecharacteristics of the specific contents, is believed to be to 205 F.

The heating step is performed at a pressure of approximately oneatmosphere. Since increased external pressures are not required in orderto prevent explosive rupture or breakage of the container, it isbelieved apparent that the present method is particularly advantageouswhere such containers take the form of flexible bags or wrappers. Theheating operation is continued at approximately atmospheric pressureuntil all organisms, including spores, are killed, the interval fallingwithin the range of 24 hours to 200 or more hours.

The effectiveness of the sterilization procedure, and the details ofspecific applications of the operative procedure, will be evident fromthe following illustrative examples:

EXAMPLE I Five 6 ounce bottles were each filled with tap water from thesame source and were sealed. Prior to sealing Bacillusstearothermophilus spore strips from the same lot were placed in thebottles, each spore strip being in direct contact with the watercontained therein. Thereafter, four of the bottles and their contentswere heated at 175 F. (i 3) for 7, 8, l and 13 days, respectively. Theremaining bottle, used as a control, was maintained at room temperature.Following such treatment, each of the bottles was opened and its sporestrip examined for growth. None of the four spore strips in the bottleswhich had been heated showed any evidence of growth and none revealedany viable micro-organisms. Evidence of spore growth was clearlyapparent on the spore strip of the control.

EXAMPLE II The procedure of Example I was repeated except that thebottles (2) were heated for 4 and 6 days, respectively, at a temperatureof 175 F. 5). The Bacillus stearothermophilus spore strips in both ofthe heated bottles and in the control revealed evidence of sporeviability. The combined results of Examples 1 and It therefore revealedthat sterilization, as evidenced by the destruction of Bacillusstearothermophilus, occurs in a period of over 6 days when ordinary tapwater is heated at a temperature of approximately 175 F.

EXAMPLE lll lsotonic saline was sealed in four foil wrappers eachcontaining approximately 30 cc of such liquid. Prior to sealing, aBacillus stearothermophilus spore strip was inserted into each package.Three of the packages were heated to 200 F. (1 3) and at atmosphericpressure; the remaining package was left unheated and used as a control.Two of the packages, heated for 3 and 4 days, respectively, containedspore strips with viable micro-organisms. Such viability was alsoevidenced by the spore strip of the control. However, the spore stripfor the remaining package, heated continuously for 6 days, revealed noviable spores.

EXAMPLE IV where such viability was apparent.

EXAMPLE V Reportedly polluted water, taken from the White River inIndianapolis, Indiana, was placed in four 200 cc bottles and the bottleswere then sealed. One was used as a control; the remaining 3 bottleswere heated at F. (t 3") for 3, 4, and 5% days, respectively.Thereafter, the contents of the bottles were filtered through Milliporefilter pads and were incubated to culture the micro-organisms retainedthereby. Examination of the pads revealed no viable micro-organisms onthose pads through which liquid had been filtered from bottles heatedfor 4 and 5% days, respectively. Viable spores were present on thosepads moistened by the contents of the control bottle and by the contentsof the bottle heated for 3 days.

EXAMPLE Vl Seven amber glass bottles, each of approximately 6 ouncecapacity, were half filled with distilled water. Bacillusstearothermophilus spore strips from the same batch were secured to thecovers for each of the bottles and the bottles were then sealed so thatthe spore strips were suspended in the upper portions of the bottles outof direct contact with the liquid. One bottle was used as a control; theremaining 6 were heated at 200 F. (2': 3) for l, 2, 3, 4, 5 and 6 days,respectively. The spore strips of the control (which had been maintainedat room temperature) and the bottle which had been heated for only oneday revealed viable microorganisms. The spore strips of the bottlesheated for 2 days or more revealed no viable spores.

The test was repeated using Bacillus subtilis (Globigii) spore strips.Again, the spore strips in the control bottle and in the bottle heatedfor one day carried viable spores; all of the remaining bottles (i.e.,those heated for 2 days or more) contained spore strips which revealedno viable spores following such treatment.

EXAMPLE Vll Two groups of identical laparotomy sponges were used in thefollowing test. Each sponge consisted of 20 layers of creped absorbentpaper encased in a liquidpermeable spun-bonded nylon-polyethylenelaminate marketed under the designation Cerex by Monsanto Company, St.Louis, Mo. Into the center of each sponge was placed a spore strip, onegroup of l l sponges containing B. stearotherrnophilus spore strips andthe other group of l l sponges containing B. subtilis (Globigii) sporestrips. Thereafter, each of the sponges was moistened slightly withdistilled water (to approximately 50 percent of its total weight) andsealed in an aluminum foil wrapper. The packages were then heated at atemperature of over F. and under 200 F. for the intervals set forth inthe following tables, and with the results as indicated. Negativeresults mean that no viable spores were present on the strips followingtreatment.

B. Stearothennophilus Item Heating Time (days) Results l l positive 2 2negative 3 3 ll 0 (control) positive B. Globigil Item Heating Time(days) Results I 1 negative 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 l0 l0 l l 0(control) positive While in the foregoing we have disclosed anembodiment of the invention in considerable detail for purposes ofillustration, it will be understood by those skilled in the art thatmany of these details may be varied without departing from the spiritand scope of the invention.

we claim:

1. A method of sterile packaging comprising the steps of sealing aproduct comprising a liquid which is at least predominately water withina container capable of withstanding exposure to temperatures up to 212F. at atmospheric pressure, and heating said container and its contentsfor at least 24 hours at a temperature above l F. and below 212' F., andbelow the boiling temperature of said liquid, until the containersinterior surfaces and its contents are sterilized.

2. The method of claim 1 in which said contents also includes a solidarticle capable of withstanding temperatures up to 212 F.

3. A method of sterile packaging comprising the steps of sealing aproduct comprising a liquid which is at least predominately water withina container capable of withstanding exposure to temperatures up to theboiling point of water at atmospheric pressure, and heating saidcontainer and its contents at approximately atmospheric pressure and forat least 24 hours at a temperature above l70 F. and below 212 F., andbelow the boiling temperature of said liquid, until the container'sinterior surfaces and contents are sterilized.

4. The method of claim 3 in which said heating falls within the range ofI to 205 F.

5. The method ofclaim 3 in which said product comprises a solid articleto be sterilized, said contents of said container also including a gascontaining water vapor.

* i t i t

2. The method of claim 1 in which said contents also includes a solidarticle capable of withstanding temperatures up to 212* F.
 3. A methodof sterile packaging comprising the steps of sealing a productcomprising a liquid which is at least predominately water within acontainer capable of withstanding exposure to temperatures up to theboiling point of water at atmospheric pressure, and heating saidcontainer and its contents at approximately atmospheric pressure and forat least 24 hours at a temperature above 170* F. and below 212* F., andbelow the boiling temperature of said liquid, until the container''sinterior surfaces and contents are sterilized.
 4. The method of claim 3in which said heating falls within the range of 190* to 205* F.
 5. Themethod of claim 3 in which said product comprises a solid article to besterilized, said contents of said container also including a gascontaining water vapor.